Contact lens and method and systems for constructing a contact lens

ABSTRACT

Contact lenses, methods and systems for accomplishing the requirement for biocompatibility of oxygen delivery to the eye, and the cornea in particular, when elements and components are used which reduce the transmissibility of oxygen and which require coverage of a significant area of the non-vascularized cornea. A contact lens assembly is provided, comprising: an anterior surface, a posterior surface and at least one element or component having a substantially low oxygen permeability disposed within the lens. The contact lens also includes a layer having an oxygen permeability greater than the aforementioned element or component. The thickness of this layer is such that the layer provides an equivalent oxygen percentage to the cornea beneath the aforementioned element or component.

CROSS REFERENCE TO RELATED APPLICATIONS

This claims the benefit of U.S. patent application Ser. No. 14/878,475filed on Oct. 8, 2015, which in turn claims the benefit of U.S. Prov.Pat. App. Nos. 62/061,270 and 62/063,490 filed on Oct. 8, 2014 and Oct.14, 2014, respectively, the entireties of which are hereby incorporatedby reference.

BACKGROUND OF THE INVENTION Field of the Invention

This invention relates to the general field of contact lenses, and morespecifically toward a contact lens having at least one element orcomponent with a property rendering low or no gas permeability while atthe same time delivering a minimum amount of oxygen to the cornea of aneye wearing the contact lens.

The earliest reference to eyeborne optics is credited to LeonardoDaVinci for his envisioning of the value of placing optics on the eye.The first application was with glass scleral shells nearly 400 yearslater. The advent of plastics, particularly polymethylmethacrylate(PMMA) launched the era of corneal contact lenses wherein the materialmade contact with the cornea only. PMMA was characterized as having nogas permeability. Lenses required designs that allowed for fluidexchange behind the lens for oxygen delivery to the cornea. The decadeof the 1970's became a period of development of gas permeable rigidpolymers for corneal contact lenses. Lens designs were modified to acloser lens-eye relationship with resultant improvement of lens comfort.The modal amount of clearance and movement for non-gas permeable lensescould be decreased as the gas permeability of materials and theresultant oxygen transmissibility increased.

Gas permeability or more relevant to this discussion, oxygenpermeability is mathematically described using the coefficient Dk, whereD being diffusivity (cm²/sec), a measure of how fast the oxygen movesthrough the material, and k being the solubility (ml O²/ml ofmaterial×mm Hg), a measure of how much oxygen is contained in thematerial. The coefficient of oxygen transmissibility (Dk/t or Dk/L) isderived by dividing the oxygen permeability of a material by thethickness of the material in millimeters.

The wearing of contact lenses can cause physiological and evenpathological ocular changes to occur. These changes involve both ocularstructure and function, and hypoxia has been implicated in theiretiologies. Normal corneal metabolism and physiological function aremaintained only with an adequate supply of oxygen. Contact lensparameters are important in determining the oxygen tension between thecornea and the contact lens and whether or not the cornea is beingsupplied adequate amounts of oxygen during the wearing of these lenses.While wearing a rigid contact lens, there are two ways in which oxygencan be delivered to the cornea: transmission through the lens materialitself or through the pumping of tears (bulk-flow volume exchange andstirring) beneath the contact lens during blinking Rigid contact lensescan be manufactured in a variety of designs to achieve appropriatecentration, movement, and tear exchange.

In order to determine how well the cornea is securing oxygen duringcontact lens wearing, a Clark-type polarographic oxygen electrode can beused. Hill and Fatt made the first in vivo measurement of oxygenconsumption from the atmosphere by the human cornea in 1963. Thistechnique has revealed an increase in epithelial oxygen uptake rateafter disruption of the anterior (atmospheric) oxygen supply. Thisincreased oxygen uptake rate is greater if a contact lens is impermeableto oxygen or if it is worn statically (without blinking) The measurementof corneal oxygen uptake can be used to indicate a reduction of oxygenreaching its epithelial surface, reflected as an increase in oxygenuptake rate. Differences (reductions) in oxygen uptake rates measuredbetween static (without blinking) and dynamic (with blinking) conditionsprovide a measure of tear pump efficiency.

In 1995, Fink, Smith, and Hill measured corneal oxygen uptake rates ontwelve human subjects following eleven deprivation intervals, rangingfrom 0 to 300 seconds in 30 second steps. The oxygen deprivation wasinduced by the static wearing of polymethylmethacrylate (PMMA) contactlenses, which are impermeable to oxygen. It was found that the humancornea, when stressed by a reduction in oxygen availability,demonstrates two modes of oxygen uptake. The oxygen uptake ratesassociated with deprivation intervals between 0 and 90 seconds increasedmuch more rapidly with deprivation interval than did the oxygen uptakerates associated with deprivation intervals from 120 to 300 seconds. Theslope of the oxygen uptake rate versus wearing time function associatedwith contact lens wearing times between 120 to 300 seconds was notsignificantly different from zero. After 300 seconds of static PMMAcontact lens wearing, the oxygen uptake rate was 6.32 times that of thenormal open eye. Measurement of corneal oxygen uptake in 30 secondintervals following contact lens removal showed a steady return tobaseline values, so that by 300 seconds following lens wearing, theoxygen uptake rates were not significantly different from the baselinevalues.

Past studies have shown that contact lens material and design caninfluence the corneal oxygen uptake rates measured after static wearingof contact lenses. Contact lenses fitted to parallel the cornealcurvature result in the greatest central corneal oxygen debt after shortperiods of static lens wearing, compared to steeper and flatter fits.Lenses shorter in radius of curvature (steeper) provide for a volume oftears between the contact lens and central cornea, whereas lenses withlonger curvature radii (flatter) might result in slight movement ordecentering that could provide oxygenated tears from the annulus oftears in the lens periphery. At least three separate studies, using thePMMA material, have demonstrated the influence of lens diameter on thecorneal oxygen uptake rates measured after the static wearing of contactlenses. In one study, overall diameter varied from 8.2 to 9.4 mm in0.3-mm steps. Optic zone diameter was 1.4 mm smaller than the overalldiameter, so as to maintain a constant peripheral curve width. Theincrease in sagittal depth resulted in steeper fitting lenses, increasedtear pooling, and reduction in post-exposure corneal oxygen uptakerates.

In a second study, the optic zone diameter was held constant at 7.4 mm,whereas overall diameter varied from 8.2 to 10.0 mm in 0.3 mm steps.Post-exposure corneal oxygen uptake rates were not significantlydifferent among these designs, because the volume of tears over thecentral cornea remained constant. In the third study, a constant tearlayer thickness was maintained as overall and optic zone diametersvaried (from 7.6 to 10.6 mm for overall diameter, with optic zonediameter being 1.4 mm smaller) by varying the base curve radius. The twosmallest lenses were associated with significantly lower oxygen uptakerates than those obtained with the two largest lenses, indicating thatcentral corneal oxygen demand can increase as more of the cornea iscovered. Other studies have shown that changes in axial edge lift andcontact lens power, while keeping all other parameters constant, do notaffect corneal oxygenation under the static wearing of non-gas-permeablecontact lenses.

Several studies have demonstrated that increasing the oxygentransmissibility of contact lenses will result in reduction inpost-exposure corneal oxygen uptake rates. Lens material also influencesthe oxygen supply to the cornea. Increasing material permeability (Dk)or decreasing lens thickness (t) will increase lens transmissibility(Dk/t) and oxygen supply to the cornea. While lenses of the samecalculated Dk/t values, but of different Dk and t combinations shouldevoke the same corneal oxygen uptake response, it has been shown thatthis does not necessarily happen.

It has been reported that, when a gas permeable hydrophilic contact lensis sandwiched between the cornea and an impermeable PMMA lens, theoxygen dissolved in the hydrogel lens serves as a reservoir of oxygen tothe cornea during periods of oxygen deprivation. The cornea can drawdissolved oxygen from the contact lens for a few minutes, until theoxygen supply in the lens is exhausted. It is possible to detect thisreservoir effect in both hydrogel and rigid gas permeable lenses. Thick,high Dk rigid gas permeable lenses result in less change in cornealoxygen uptake (compared to the non-lens-wearing eye) than did thin,lower Dk lenses of the same Dk/t.

Holden and Mertz generated criteria for minimum oxygen transmissibilityfor maintenance of normal corneal physiology for wearing contact lenseswith an open eye (daily wear) and for wearing lenses with normalovernight periods of sleep (extended wear or continuous wear).

Holden and Mertz studied the critical oxygen levels to avoid cornealedema and defined them in terms of oxygen transmissibility andequivalent oxygen percentage. The relationship between corneal edema andhydrogel lens oxygen transmissibility was examined for both daily andextended contact lens wear by measuring the corneal swelling responseinduced by a variety of contact lenses over a 36 hour wearing period.The relationships derived enabled average edema levels that occur withdaily and extended wear in a population of normal young adults to bepredicted to within ±1.0%. The critical lens oxygen transmissibilityrequired to avoid edema for daily and extended contact lens wear wereobtained from the derived curves. Holden and Mertz found under dailywear conditions that lenses having an oxygen transmissibility of atleast 24.1±2.7×10⁻⁹ (cm×ml O₂)/(sec×ml×mmHg), an Equivalent OxygenPercentage (EOP) of 9.9%, did not induce corneal edema. The criticalhydrogel lens oxygen transmissibility needed to limit overnight cornealedema to 4% (the level experienced without a contact lens in place) wasfound to be 87.0±3.3×10⁻⁹ (cm×ml O₂)/(sec×ml×mmHg), an EOP of 17.9%.

Soft hydrophilic materials were developed about a decade before thefirst gas permeable rigid materials. The first soft hydrophilicmaterials had low oxygen permeability (poly-2hydroxyethyl methacrylate).The gas permeability of conventional hydrogel materials was increasedover the next three decades primarily by increasing water content.Lenses were classified as having low or high water content and whetherthe materials were ionic or non-ionic. The polymers fell into fourclasses. It was generally understood that ionic polymers of negativecharge demonstrated higher rates of deposition. Further, it wasunderstood that high water lenses demonstrated a greater tendency forcorneal staining. One explanation is a possible higher rate of loss ofwater content. Increased thickness intended to control the loss of waterfrom the lens was incorporated and observations of reduced cornealstaining were reported.

Silicone hydrogel materials were developed during the 1990's in aneffort to significantly increase the gas permeability of soft contactlenses with the hope that increased oxygen transmissibility would resultin a reduction of adverse events and an increase in comfort and positiveoverall user experience. The water content of popular materials rangedfrom approximately 25% to as high as approximately 75%. These materialsare relatively hydrophobic and surface modification in the form ofplasma treatment improved their in vitro and in vivo surface wetting.Silicone hydrogel lenses constitute the majority of new contact lensprescriptions, with conventional hydrogel making up a significantportion of new contact lens prescriptions as well. Hybrid contact lenseshaving a rigid gas permeable center and a soft annular skirt, as well asrigid corneal and scleral lenses, each make up a very small portion ofnew contact lens prescriptions.

The oxygen permeability (Dk) of silicone hydrogel materials ranges fromapproximately 50×10⁻¹¹ (cm²/sec) (mL O₂)/(mL×mm Hg) to approximately180×10⁻¹¹ (cm²/sec) (mL O₂)/(mL×mm Hg). Some market leading lenses aredesigned with harmonic thicknesses in the range of 0.12 to 0.18 mm. Amodal lens with commercial success has a Dk/t of greater than 80×10⁻⁹(cm×ml O₂)/(sec×ml×mmHg). Efforts are made to keep a thin lens profileto allow for optimum oxygen transmissibility.

During the late 1970's, Dow Corning developed silicone elastomer softlenses using polydimethylsiloxane (PDMS) having a water content ofapproximately 0.2%. Dow Corning of Midland, Mich. marketed the Silsoft®(elastofilcon A) contact lens for adult aphakia for up to 30 days ofwear in early 1982. The lens material had been approved by FDA in July1981 for daily wear and Aphakic Extended wear in September 1981. Thelens had an oxygen permeability (Dk) of about 340×10⁻¹¹ (cm²/sec) (mLO₂)/(mL×mm Hg). Silicone elastomer lenses were cast molded and thenplasma treated to obtain surface wettability.

This silicone elastomer material was also sold under the brand nameSilsight and was introduced for 30 day extended wear for non-aphakicrefractive error correction. Silsight lenses were used for daily orextended wear and had a reported five percent rate of corneal adherence,a long referred to risk with silicone elastomer lenses. Ninety eightpercent of 616 patients were reported to have 20/25 or better visualacuity with this lens. It was reported that there were no significantchanges in corneal physiology with the elastifilcon A lens used forextended wear in myopic patients in over 400 patients. Previous siliconeelastomer lenses in Germany and Japan had reported eight to twenty-twopercent non-movement or adherence. Other side effects reported withthese lenses included occasional and random hydrophobicity, which wouldblur vision but not irritate the eye. A lens made of this material withimproved manufacturing was, according to this report, likely to allowexcellent corneal health and very good vision compared to hydrogellenses.

Recently, The Infant Aphakic Treatment Study, sponsored by the NationalEye Institute and National Institutes of Health (NIH), was completedwith one year and then five year follow-up. The Silicone Elastomercontact lenses were worn successfully with relatively few adverse eventsby a cohort of infants with unilateral aphakia. There were significantlymore adverse events and additional intraoperative procedures in theintraocular lens (IOL) group. None of the contact lens—related adverseevents resulted in central corneal scars that were judged to permanentlyaffect visual acuity. These results indicate, under very difficultconditions, the safety and efficacy of the silicone elastomer contactlens.

The investigators concluded that when weighing whether to operate on aninfant younger than 7 months of age with a unilateral cataract, it wasrecommended to leave the eye aphakic and to correct the focusing errorof the eye with a contact lens. They added that, primary IOLimplantation should be reserved for those infants where, in the opinionof the surgeon, the cost and handling of a contact lens would be soburdensome as to result in significant periods of uncorrected aphakia.

Silicone elastomer (such as polydimethylsiloxane, or PDMS) is an idealmaterial for embedded components. The PDMS material is reported to beused in the SENSIMED Triggerfish contact lens, which has a strain gaugeand sending unit implanted in the lens to measure intraocular pressure.The components are in the periphery of the lens and represent minimalinterference with oxygen transmissibility. The high oxygen permeabilityof PDMS is ideal for supporting corneal physiology. Modern surfacemodification is expected to reduce the hydrophobicity of the earlierPDMS lenses. Further, PDMS formulation and curing process has beentested and found to be non-cytotoxic, non-systemic toxic, and anon-ocular irritant.

The use of ultra-high oxygen permeable materials presents a paradoxicalopportunity to increase thickness of a layer beneath a low or non-gaspermeable component to increase the equivalent oxygen percentage to thesurface of the cornea covered by the component. Conventional practice asaforementioned constructs lenses thinner to increase oxygentransmissibility since the formula for transmissibility is thepermeability divided by the thickness. If this practice were applied toa layer posterior to a low or non-gas permeable component, the oxygenpercentage beneath the component would decrease. Nine percent (9%) isestablished as the minimum for open eye or daily wearing for particularembodiments of the present invention.

There are references that disclose layered lens constructions thatinclude a cavity or chamber for retaining a component, a fluid or a gel.The oxygen permeability of the previously taught aqueous solutions issubstantially lower than that of the polymers intended for theembodiments of the present disclosure. While some of the prior artreferences have merit for delivering oxygen, the complexity offabricating lenses described by the art is far more challenging.Biocompatibility and management of the integrity of the aqueous or gelfilled cavities is also troublesome.

The prior art has also taught an air cavity with an anterior gaspermeable layer at its periphery and an underlying posterior gaspermeable layer intended to deliver oxygen to the underlying eye in thepresence of non-gas permeable component anterior to the cavity. However,these references fail to teach the modulation of the thickness of apolymer layer alone for the purpose of delivering a desired equivalentoxygen percentage to a predetermined location on the corneal surface.

Reports of the inclusion of elements or components into contact lenseshave been made in recent years. These elements include filters, lightemitting diodes (LED), light sources, sensors, strain gauges,processors, sending units, wires and batteries. The reports include theuse of graphene for night vision display applications. In many cases,like the use of graphene, titanium pin-hole apertures, low gas permeablepolarizer filters, LED and organic LED (OLED) arrays, and dielectricstack filters, the respective elements or components are not gaspermeable or demonstrate low permeability. Thus, there has existed aneed for a device, system and method for incorporating the at least oneelement or component which has an oxygen permeability lower than thematerial of the lens body in contact lenses and at the same time deliveroxygen to the eye in the region covered by the at least one element orcomponent which has an oxygen permeability lower than the material ofthe lens body.

SUMMARY OF THE INVENTION

The current invention provides just such a solution by having contactlenses, methods and systems for accomplishing the requirement forbiocompatibility of oxygen delivery to the eye and the cornea inparticular when components, also referred to as elements, are used whichreduce the transmissibility of oxygen and which require coverage of asignificant area of the non-vascularized cornea.

In one embodiment, a contact lens assembly is provided, comprising: ananterior surface, a posterior surface and at least one element orcomponent having a substantially low oxygen permeability disposed withinthe lens. The contact lens also includes a layer having an oxygenpermeability greater than the aforementioned element or component. Thethickness of this layer is such that the layer provides an equivalentoxygen percentage to the cornea beneath the aforementioned element orcomponent.

It is an object of the invention to provide a contact lens with athickness of the material beneath the low or non-gas permeable componentto increase the equivalent oxygen percentage to the corneal surfacebeneath the component

It is another object of the invention to provide a method for making acontact lens with an optimum thickness of a layer of material beneath alow or non-gas permeable component such that a minimum requirement ofoxygen delivery for the physiologic requirements of the cornea is met.

It is a further object of this invention to provide an improved contactlens and method for making the same that incorporates a low or non-gaspermeable component while providing the minimum requirement of oxygendelivery for the physiologic requirements of the cornea.

Terms and phrases used in this document, and variations thereof, unlessotherwise expressly stated, should be construed as open ended as opposedto limiting. As examples of the foregoing: the term “including” shouldbe read as meaning “including, without limitation” or the like; the term“example” is used to provide exemplary instances of the item indiscussion, not an exhaustive or limiting list thereof; the terms “a” or“an” should be read as meaning “at least one,” “one or more” or thelike; and adjectives such as “conventional,” “traditional,” “normal,”“standard,” “known” and terms of similar meaning should not be construedas limiting the item described to a given time period or to an itemavailable as of a given time, but instead should be read to encompassconventional, traditional, normal, or standard technologies that may beavailable or known now or at any time in the future. Likewise, wherethis document refers to technologies that would be apparent or known toone of ordinary skill in the art, such technologies encompass thoseapparent or known to the skilled artisan now or at any time in thefuture. Furthermore, the use of plurals can also refer to the singular,including without limitation when a term refers to one or more of aparticular item; likewise, the use of a singular term can also includethe plural, unless the context dictates otherwise.

The presence of broadening words and phrases such as “one or more,” “atleast,” “but not limited to” or other like phrases in some instancesshall not be read to mean that the narrower case is intended or requiredin instances where such broadening phrases may be absent. Additionally,the various embodiments set forth herein are described in terms ofexemplary block diagrams, flow charts and other illustrations. As willbecome apparent to one of ordinary skill in the art after reading thisdocument, the illustrated embodiments and their various alternatives canbe implemented without confinement to the illustrated examples. Forexample, block diagrams and their accompanying description should not beconstrued as mandating a particular architecture or configuration.

The following references are considered pertinent to the currentdisclosure, and their entireties are incorporated herein by reference:

-   -   Kennedy R H, Bourne W M, Dyer J A. A 48-year clinical and        epidemiologic study of keratoconus. Am J Ophthalmol 1986;        101:267-273.    -   Korb D R, Finnemore V M, Herman J P. Apical changes and scarring        in keratoconus as related to contact lens fitting techniques.        Journal of the American Optometric Association 1982; 53:199-205.    -   Maguen E, Espinosa G, Rosner I R, Newburn A B. Long-term wear of        Polycon contact lenses in keratoconus. The CLAO Journal 1983;        9:57-59.    -   Drews M J, Driebe W T, Stern G A. The clinical management of        keratoconus: a 6-year retrospective study. CLAO J 1994;        20:194-197.    -   Smiddy W E, Hamburg T R, Kracher G P, Stark W J. Keratoconus:        contact lens or keratoplasty? Ophthalmology 1988; 96:487-492.    -   Westerhout D. The combination lens. Contact Lens 1973; 4(5):3-9.    -   Baldone J A. The fitting of hard lenses onto soft contact lenses        in certain diseased conditions. Contact Lens Med Bull 1973;        6(2-3):15-17.    -   Weissman B A. An old-new piggyback fit. Contact Lens Forum 1982;        7(3):71-73.    -   Brennan N A. Current thoughts on the etiology of ocular changes        during contact lens wear. Australian J Optom 1985; 68(1):8-24.    -   Hill R M, Fatt I. Oxygen uptake from a reservoir of limited        volume of the human cornea in vivo. Science 1963; 142:1295-1297.    -   Hill R M. Cuklanz H. Oxygen transmissivity of membranes in        contact with the cornea: physiological observations. Br J        Physiol Optics 1967; 24(3):206-216.    -   Fink B A, Smith B J, Hill R M. Oxygen depletion characteristic        of in vivo human cornea [ARVO Abstract]. Invest Ophthalmol Vis        Sci 1995; 36(4):5310.    -   Hill R M, Fatt I. Oxygen deprivation of the cornea by contact        lenses and lid closure. Am J Optom Amer Acad Optom 1964;        41(11):678-687.    -   Fink B A, Hill R M, Carney L G. Influence of rigid contact lens        base curve radius on tear pump efficiency. Optom Vis Sci 1992;        69:60-5.    -   Fink B A, Hill R M, Carney L G. Influence of rigid contact lens        overall and optic zone diameters on tear pump efficiency. Optom        Vis Sci 1990; 67:641-4.    -   Fink B A, Carney L G, Hill R M. Rigid contact lens design:        effects of overall diameter changes on tear pump efficiency.        Optom Vis Sci 1991; 68:198-203.    -   Fink B A, Carney L G, Hill R M. Rigid lens tear pump efficiency:        effects of overall diameter/base curve combinations. Optom Vis        Sci 1991; 68:309-313.    -   Fink B A, Hill R M, Carney L G. Effects of rigid contact lens        edge lift changes on tear pump efficiency. Optom Vis Sci 1991;        68:409-13.    -   Fink B A, Carney L G, Hill R M. Influence of power changes in        single cut rigid contact lenses on tear pump efficiency. Optom        Vis Sci 1992; 69:691-7.    -   Hill R M, Szczotka L B. Hypoxic stress units: another look at        oxygen performance of RGP lenses on the cornea. Contact Lens        Spectrum 1991; 6(4):31-3.    -   Ostrem E D, Fink B A, Hill R M. Contact lens transmissibility:        effects on delivery of oxygen to the cornea. Optom Vis Sci 1996;        73:159-63.    -   Fink B A, Hill R M, Smith B, Szczotka L, Barr J T. RGP materials        that reduce hypoxic stress: Part II. Contact Lens Spectrum 1992;        7(4):20-1.    -   Hill R M. Aqualunging: or the lens reservoir effect. Inter        Contact Lens Clin 1981; 8(6):30-35.    -   Fink B A, Hill R M, Pappas C. Dk/L: effect on the post-lens        reservoir [ARVO Abstract]. Invest Ophthalmol Vis Sci 1999;        40(4):5906. Abstract #4775.    -   Holden B A, Mertz G W. Critical oxygen levels to avoid corneal        edema and daily and extended wear contact lenses Invest        Ophthalmol Vis Sci 25:1161-1167, 1984    -   TRIAL REGISTRATION, clinicaltrials.gov, Identifier: NCT00212134

A particular embodiment of the current disclosure is a contact lenscomprising an anterior surface facing away from an eye; a posteriorsurface facing toward the eye; a medium residing between the anteriorsurface and the posterior surface, where the medium has an oxygenpermeability; a component, where the component has an oxygenpermeability lower than the oxygen permeability of the medium; and alayer between the component and the posterior surface, where the layercomprises a material with a thickness, where the thickness of thematerial of the layer is sufficient to deliver an oxygen percentage to alocation on the surface of the cornea, where the material of the layeris contiguous with the medium residing between the anterior surface andthe posterior surface.

Another embodiment of the current disclosure is a method of determininga thickness of a polymer layer of a contact lens, where the lenscomprises an anterior surface facing away from an eye; a posteriorsurface facing toward the eye; a medium residing between the anteriorsurface and the posterior surface, where the medium has an oxygenpermeability; a component, where the component has an oxygenpermeability; and the polymer layer, where the polymer layer has anoxygen permeability; the method comprising the step of: determining anarea of a cornea covered by the component; calculating the thickness ofthe polymer layer using the oxygen permeability of the polymer layer,the area of the cornea covered by the component, the oxygen permeabilityof the component; the oxygen permeability of the medium; and a desiredoxygen percentage to be delivered to a desired location on the cornealsurface.

A further embodiment of the current disclosure is a contact lenscomprised of: a lens body having an anterior surface facing away from aneye and a posterior surface facing toward an eye, where the lens bodycomprises a medium between the anterior surface and a posterior surface;one or more components within the medium, where the one or morecomponents have an oxygen permeability lower than the medium of the lensbody; and a polymer layer between the one or more components and theposterior surface; wherein, the polymer layer has a thickness sufficientto deliver a pre-determined oxygen percentage to a pre-determinedlocation on the surface of a cornea and is contiguous with the medium ofthe lens body that proceeds in an anterior direction to the anteriorsurface of the lens body.

Yet another embodiment of the current disclosure is a method ofdetermining a thickness of a polymer layer of a contact lens having: alens body having an anterior surface facing away from an eye and aposterior surface facing toward an eye, where the lens body comprises amedium between the anterior surface and a posterior surface; where thelens body further comprises a component which has an oxygen permeabilitylower than the medium of the lens body; and where the lens body furthercomprises a polymer layer between the component and the posteriorsurface, where the polymer layer has an oxygen permeability; wherein,the thickness of the polymer layer is mathematically calculated usingthe oxygen permeability of the polymer layer, the area of a corneacovered by the component, an oxygen transmission through the component,an oxygen transmissibility of the lens body surrounding the componentsand a predetermined oxygen percentage to be delivered to apre-determined location on the surface of the cornea.

An additional embodiment of the current disclosure is a contact lenscomprised of: an anterior surface facing away from an eye; a posteriorsurface facing toward an eye; a lens body containing the anterior andposterior surface and a medium between; one or more components whichhave oxygen permeabilities lower than the medium of the lens body andwhere the one or more components have a surface area of greater than 3mm²; and, a polymer layer between the one or more components and theposterior surface; wherein, the polymer layer has an oxygen permeabilityof 100×10-11 (cm²/sec) (mL O₂)/(mL×mm Hg) or greater and a thicknesssufficient to deliver an oxygen percentage of nine percent or greater tothe center of an anterior corneal surface covered by the components.

There has thus been outlined, rather broadly, the more importantfeatures of the invention in order that the detailed description thereofmay be better understood, and in order that the present contribution tothe art may be better appreciated. There are additional features of theinvention that will be described hereinafter and which will form thesubject matter of the claims appended hereto. The features listed hereinand other features, aspects and advantages of the present invention willbecome better understood with reference to the following description andappended claims.

BRIEF DESCRIPTION OF THE FIGURES

The accompanying drawings, which are incorporated in and form a part ofthis specification, illustrate embodiments of the invention and togetherwith the description, serve to explain the principles of this invention.The figures are not intended to be exhaustive or to limit the inventionto the precise form disclosed. It should be understood that theinvention can be practiced with modification and alteration, and thatthe invention be limited only by the claims and the equivalents thereof.

FIG. 1 is a cross-sectional view of a contact lens with a lens filter atthe anterior surface of the lens, in accordance with selectedembodiments of the current disclosure.

FIG. 2 is a cross-sectional view of a contact lens with two componentsat different sagittal depths in accordance with selected embodiments ofthe current disclosure.

FIG. 3 is a cross-sectional view of a contact lens with multiplecomponents at different sagittal depths in accordance with selectedembodiments of the current disclosure.

FIG. 4 is an iso-line drawing of the equivalent oxygen percentage valuesat the posterior surface of a contact lens having one component with alimited oxygen transmissibility and with a surface area defined by itsdimensions and with a posterior polymer layer with an oxygenpermeability and a thickness designed to deliver a minimum equivalentoxygen permeability in accordance with selected embodiments of thecurrent disclosure.

FIG. 5 is a flow chart for determining the thickness of a polymer layerposterior to at least one component in the lens body of a contact lensfor the purpose of delivering a predetermined equivalent oxygenpercentage to a predetermined location on the corneal surface inaccordance with selected embodiments of the current disclosure.

DETAILED DESCRIPTION OF THE INVENTION

Many aspects of the invention can be better understood with thereferences made to the drawings below. The components in the drawingsare not necessarily drawn to scale. Instead, emphasis is placed uponclearly illustrating the components of the present invention. Moreover,like reference numerals designate corresponding parts through theseveral views in the drawings.

Selected embodiments of the current disclosure include a contact lenshaving an anterior surface away from the eye and a posterior surfacefacing the eye and a lens body bordered by the anterior and posteriorsurface. The contact lens is generally described as a low modulus lens(soft); even so the invention is applicable to a high modulus lens(rigid) or a lens having both rigid and soft materials (hybrid). Theposterior surface is generally related in geometry to the ocular contourof the eye but may deviate in its shape from representing the ocularcontour of the eye. The central geometry of the anterior surface of thelens is generally selected to produce the desired refractive correctionfor the eye but could be a secondary element in providing the refractivecorrection if lenslets or apertures within the lens or other means areused to produce the refractive correction.

The body of the lens is defined as one or more lens substrate materialsbetween or including the anterior surface and the posterior surface inthe present invention. The lens body contains one or more componentswhich have an oxygen permeability lower than the material posterior tothem. The components can be on the anterior surface and/or within thebody of the lens. Portions of the components may be at differentsagittal depths on or within the body of the lens.

Selected embodiments of the current invention provide for the use of alayer of the lens polymer of the lens body or a second lens polymerposterior to at least one element or component that has an oxygenpermeability lower than the material, or medium, posterior to them. Thematerial posterior to the respective components serves to deliver oxygenby way of the oxygen transmission through the exposed anterior surfaceand lens body above the posterior layer and the thickness of thematerial of the posterior layer. The thickness of the polymer posteriorto the components which have an oxygen permeability lower than thematerial posterior to them is a function of the oxygen permeability ofthe polymer beneath the components; the surface area of the componentscovering the cornea; the oxygen transmissibility of the componentscovering the cornea; and, the targeted equivalent oxygen percentage tobe delivered to a predetermined location of the cornea.

The thickness of the polymer layer is generally greater the lower thepermeability of the material posterior to the components and the largerthe area of the components which have an oxygen permeability lower thanthe material posterior to the components. Conversely, the thickness ofthe polymer layer is generally lesser the greater the permeability ofthe material posterior to the components and the smaller the area of thecomponents which have an oxygen permeability lower than the materialposterior to the components.

Particular aspects of the current disclosure provide for increasing thelens thickness to increase the equivalent oxygen percentage delivered tothe cornea covered by an element or component having low or no oxygentransmissibility. The traditional practice taught in prior art is todecrease thickness to increase oxygen transmissibility. Materials havinga sufficiently high oxygen permeability may be used with increasedthickness to facilitate oxygen diffusion sufficient to maintain thephysiological requirements of the cornea covered by at least oneelements or component having limited or no oxygen permeability.

Since increasing the thickness decreases the oxygen transmissibility ofthe layer, the invention could not be practiced with materials having apermeability below a threshold determined by the area of the componentswhich have an oxygen permeability lower than the material posterior tothe components and the targeted equivalent oxygen percentage desired atthe specified location on the corneal surface. For example, a materialhaving a substantially low permeability and a component area covering asubstantially large area of the cornea could not be made at anythickness to deliver the Holden Mertz minimum oxygen transmissibilityfor healthy daily wear contact lenses. Particular embodiments of thecurrent disclosure are directed to contact lenses having a posteriorlayer having a permeability substantially high to allow for increasingits thickness to provide a layer for oxygen delivery. The use ofmaterials having a permeability of greater than Dk=100×10′ (cm²/sec) (mLO₂)/(mL×mm Hg) is at least substantially high enough to allow for suchan increase in thickness to provide a layer for oxygen delivery.

The Holden Mertz criteria speak to an oxygen transmissibility thatproduces a minimum of corneal swelling from hypoxia (low oxygendelivery). A mathematical model may also use a percentage of oxygen inthe gas arriving at the corneal surface as a metric for determining theappropriate thickness of the layer posterior to the component within acontact lens. Hence, the third variable is the targeted equivalentoxygen percentage to a defined location on the anterior cornea. Holdenand Mertz defined the equivalent oxygen percentage for daily wear as9.9% with a range of +/− 1% as the standard error of the estimate.Particular embodiments of the current disclosure use a target minimumequivalent oxygen percentage of 9%.

One embodiment of the present disclosure is a contact lens made of asingle polymer polydimethylsiloxane and having a round polarizer filterthat is 7 mm in diameter that has no gas permeability. The full surfacearea of the polarizer covers the cornea. The Dk of the PDMS is measuredto be 340×10⁻¹¹ (cm²/sec) (mL O₂)/(mL×mm Hg). The defined oxygenpercentage to the cornea posterior to the center of the non-gaspermeable filter is 9%. One mathematical model for calculating thepercentage of oxygen to reach the distance to the center as a functionof the thickness and Dk is:

${EOP} = {{{- \frac{1187}{D_{k}}}{\ln\left( \frac{D_{k}}{t} \right)}} + \frac{140}{\sqrt{area}}}$

For this embodiment, the filter has an oxygen transmissibility of zero,or a filter Dk/t of 0.0×10⁻⁹ (cm×mL O₂)/(sec×mL×mmHg). The filterdiameter is 7 mm (38.48 mm²); and the equivalent oxygen percentagetarget for the cornea under the center of the circular filter element is9%. In this case the thickness of the polymer layer having aDk=340×10⁻¹¹ (cm²/se c) (mL O₂)/(mL×mm Hg), and under the geometriccenter of the filter described above is calculated to be, 0.700 mm.

It is to be understood by those skilled in the art that othermathematical models could be used to define the relationship between theoxygen permeability of at least one element, the area covered by theelement, the oxygen reaching the layer beneath the element, thepermeability of the layer beneath the element, and the equivalent oxygenpercentage desired at a defined location.

Additional embodiments of the current disclosure include multipleelements or components that are non-gas permeable or having at least oneelement with gas permeability lower than the layer posterior to thesecomponents. Other embodiments include components with spaces,fenestrations or channels for the purpose of increasing their oxygentransmission. Further embodiments include multiple components withspaces between the components. In such embodiments, the average oxygentransmissibility is expected to exceed the transmissibility of thecomponent with the lowest permeability. In the respective embodiments,the thickness of the layer posterior to the elements or components ismodulated to produce the targeted oxygen percentage to the specifiedarea of the corneal surface.

Selected embodiments of the current disclosure utilize one or morepolymer layers posterior to at least one element or component having anoxygen permeability lower than the material of the body of the lenscontaining the element or component. The one or more layers can beconfigured in thickness and position for the purpose of delivering apredetermined equivalent oxygen percentage to one or more locations inthe underlying cornea.

Referring now to the figures, FIG. 1 depicts a component containingcontact lens 100 in accordance with selected embodiments of the currentdisclosure. The component containing contact lens 100 has an anteriorsurface 101, a lens body 102, and a posterior surface 103. The componentcontaining contact lens 100 comprises a component 104, generallyperipheral lens areas 105, which circumferentially surrounds the lenscomponent 104, and a layer 106, which is posterior to the component 104and contiguous with the peripheral areas 105.

With continued reference to FIG. 1, the component 104 is constructed atthe anterior surface of the contact lens 100 and the lens body 103includes a layer 106 posterior to the component 104. As will beunderstood by those of skill in the art, the component 104 is notlimited to a location at the anterior surface, to a symmetricalconfiguration, or to a uniform thickness profile, or to a centeredposition relative to the geometric center of the contact lens 100. Forexample, additional elements or a deeper placement of the element may beemployed, or a regional placement may be employed. In this manner, thelens can be customized for the inclusion of a number and variety ofelements or components and the thickness of the posterior layer can bedetermined to provide a desired equivalent oxygen percentage to thesurface of the cornea covered by the elements or components.

FIG. 2 depicts a component containing contact lens 200 in accordancewith selected embodiments of the current disclosure. The componentcontaining contact lens 200 has an anterior surface 201, a lens body202, and a posterior surface 203. The component containing contact lens200 comprises a first component 204 which is a circular component with acentral hole or space, a second component 205 at a different sagittaldepth than the first component 204, generally peripheral lens areas 206which circumferentially surrounds the lens components 204 and 205, and alayer 207, which is posterior to the components 204 and 205 andcontiguous with the peripheral areas 206.

With continued reference to FIG. 2, the component 204 is constructed atthe anterior surface of the contact lens 200 and a second component 205is deeper in the lens body 202. The lens body 202 includes a layer 207,which is posterior to the components 204 and 205. As will be understoodby those of skill in the art, the components 204 and 205 are not limitedto locations at the anterior surface or the apparent relative depths inthe lens body 202, to a symmetrical configuration, or to a uniformthickness profile, or to a centered position relative to the geometriccenter of the contact lens 200. For example, additional elements or adeeper placement of the element may be employed, or a regional placementmay be employed. In this manner, the lens can be customized for theinclusion of a number and variety of elements or components and thethickness of the posterior layer can be determined to provide a desiredequivalent oxygen percentage to the surface of the cornea covered bythese elements or components

FIG. 3 depicts a component containing contact lens 300 in accordancewith selected embodiments of the current disclosure. The componentcontaining contact lens 300 has an anterior surface 301, a lens body302, and a posterior surface 303. The component containing contact lens300 includes a first component 304, which is a first electroniccomponent, a second component 305, which is a second electroniccomponent at a different sagittal depth than the first component 304, athird component 306, which is a wire, a fourth component 307 depicting athird electronic component at a different sagittal depth than the firstcomponent 304, generally peripheral lens areas 308, whichcircumferentially surrounds the lens components 304, 305, 306 and 307,and a layer 309, which is posterior to the components 304, 305, 306 and307 and contiguous with the peripheral lens areas 308

With continued reference to FIG. 3, the components 304, 305, 306 and 307are depicted as having various relative dimensions and constructed inthe lens body 302 at various depths The lens body 302 includes a layer308 which is posterior to the components 304, 305, 306 and 307. As willbe understood by those of skill in the art, the components 304, 305, 306and 307 are not limited to locations at the apparent relative depths inthe lens body 302, to a symmetrical configuration, or to a uniformthickness profile, or to a centered position relative to the geometriccenter of the contact lens 300. For example, additional components or adeeper placement of the components may be employed, or a regionalplacement may be employed. In this manner, the lens can be customizedfor the inclusion of a number and variety of elements or components andthe thickness of the posterior layer can be determined to provide adesired equivalent oxygen percentage to the surface of the corneacovered by these elements or components.

FIG. 4 is an iso-line drawing of the equivalent oxygen percentage valuesat the posterior surface of a contact lens having one component with alimited oxygen transmissibility and with a surface area defined by itsdimensions and with a posterior polymer layer with an oxygenpermeability and a thickness designed to deliver a minimum equivalentoxygen permeability in accordance with selected embodiments of thecurrent disclosure. Contact lens 400 is shown with iso-lines ofequivalent oxygen percentage (EOP) values 401, at the posterior surface402 of a lens having one component 403 with a limited oxygentransmissibility and of a surface area defined by its dimensions andwith a posterior polymer layer with an oxygen permeability and athickness (t) 404 to deliver a minimum equivalent oxygen permeability of9%.

FIG. 5 depicts a flow chart or process 500 for determining the thicknessof a polymer layer posterior to at least one component in the lens bodyof a contact lens for the purpose of delivering a predeterminedequivalent oxygen percentage to a predetermined location on the cornealsurface. The process 500 starts by using the lens and component materialproperties 501 and the characterization of the component physicalrequirements 502 to estimate the thickness of the layer posterior to theat least one component of the present invention 503. For example, thecomponent material properties 501 include oxygen permeability, elasticmodulus, refractive index, and spectral characteristics. Continuing withthe example, component physical requirements 502 include effectiveoptical diameter, thickness, surface area, and sphericity. While theestimation of posterior thickness 503 could be a randomly guessedthickness, previous numerical simulations and final designs of lensescan be used as a guide for estimating posterior thickness. Once theposterior thickness has been estimated, the component physicalrequirements 502 and the estimated posterior thickness 503 are appliedin the process of the mechanical design 504 of the lens to produce adesign of a lens that includes, for example, the optical zone diameter,outside diameter, edge thickness, center thickness, and other designcriteria. In turn, the lens and component material properties 501 andthe mechanical design of the lens 504 are integrated into themathematical calculation or numerical simulation 505 to determine aresultant equivalent oxygen percentage across the posterior surface ofthe lens. The calculated equivalent oxygen percentage across theposterior surface of the lens is compared 506 to the targetedrequirement. A successful passing, for example the resulting orcalculated equivalent oxygen percentage across the posterior surface ofthe lens is greater than a targeted requirement or within a targetedrange, advances the process to a final design 507. Failure 508 to meetthe targeted equivalent oxygen percentage returns the process to lensmechanical design 504 and reintegration of component material properties501, including varying the posterior thickness to be larger or smallerto exceed the targeted requirement or fall within a target range. Forexample, should the resulting equivalent oxygen percentage fall below atargeted requirement of 9%, the mechanical design of the lens ismodified to increase the posterior thickness and a numerical simulationis performed again on the revised design to determine a resultingequivalent oxygen percentage across the posterior surface of the lens.

While various embodiments of the present invention have been describedabove, it should be understood that they have been presented by way ofexample only, and not of limitation. Likewise, the various diagrams maydepict an example architectural or other configuration for theinvention, which is provided to aid in understanding the features andfunctionality that can be included in the invention. The invention isnot restricted to the illustrated example architectures orconfigurations, but the desired features can be implemented using avariety of alternative architectures and configurations.

Indeed, it will be apparent to one of skill in the art how alternativefunctional configurations can be implemented to implement the desiredfeatures of the present invention. Additionally, with regard to flowdiagrams, operational descriptions and method claims, the order in whichthe steps are presented herein shall not mandate that variousembodiments be implemented to perform the recited functionality in thesame order unless the context dictates otherwise.

Although the invention is described above in terms of various exemplaryembodiments and implementations, it should be understood that thevarious features, aspects and functionality described in one or more ofthe individual embodiments are not limited in their applicability to theparticular embodiment with which they are described, but instead can beapplied, alone or in various combinations, to one or more of the otherembodiments of the invention, whether or not such embodiments aredescribed and whether or not such features are presented as being a partof a described embodiment. Thus, the breadth and scope of the presentinvention should not be limited by any of the above-described exemplaryembodiments

That which is claimed:
 1. A contact lens comprising an anterior surface;an opposing posterior surface; a low or non-gas permeable componentresiding between the anterior surface and the posterior surface; and apolymer layer between the component and the posterior surface, where thepolymer layer has a thickness and an oxygen permeability of 100×10⁻¹¹(cm²/sec) (mL O₂)/(mL×mm Hg) or greater; where the component has anoxygen permeability lower than the oxygen permeability of the polymerlayer; where the thickness of the polymer layer is sufficient to deliveran equivalent oxygen percentage of nine percent or greater to a locationon a corneal surface.
 2. The contact lens of claim 1, where thethickness of the polymer layer is proportional to the oxygenpermeability of the polymer layer, an area of the corneal surfacecovered by the component, and the equivalent oxygen percentage requiredat the location on the corneal surface.
 3. The contact lens of claim 1,where the polymer layer consists of a single polymer material.
 4. Thecontact lens of claim 1, wherein the oxygen permeability of thecomponent is zero.
 5. The contact lens of claim 1, wherein the componenthas a surface area greater than 38.48 mm².
 6. The contact lens of claim1, wherein the component has a surface area greater than 7.1 mm².
 7. Thecontact lens of claim 1, further comprising a second component, wherethe second component has an oxygen permeability lower than the oxygenpermeability of the polymer layer.
 8. The contact lens of claim 1,wherein the thickness of the polymer layer is 0.7 mm.
 9. A method ofdetermining a thickness of a polymer layer of a contact lens, where thelens comprises an anterior surface; an opposing posterior surface; a lowor non-gas permeable component residing between the anterior surface andthe posterior surface; and a polymer layer between the component and theposterior surface; where the polymer layer has a thickness and an oxygenpermeability, where the component has an oxygen permeability lower thanthe oxygen permeability of the polymer layer, the method comprising thesteps of: estimating a first thickness of the polymer layer; performinga mathematical calculation or numerical simulation using the firstthickness to determine a first resulting equivalent oxygen percentageacross the posterior surface; comparing the first resulting equivalentoxygen percentage across the posterior surface to a targeted range ofacceptable equivalent oxygen percentages; estimating a second thicknessthat is larger than the first thickness if the first resultingequivalent oxygen percentage across the posterior surface is below thetargeted range of acceptable equivalent oxygen percentages; performing amathematical calculation or numerical simulation using the secondthickness to determine a second resulting equivalent oxygen percentageacross the posterior surface; comparing the second resulting equivalentoxygen percentage across the posterior surface to the targeted range ofacceptable equivalent oxygen percentages; estimating a third thicknessthat is smaller than the first thickness if the first resultingequivalent oxygen percentage across the posterior surface is above thetargeted range of acceptable equivalent oxygen percentages; performing amathematical calculation or numerical simulation using the thirdthickness to determine a third resulting equivalent oxygen percentageacross the posterior surface; and comparing the third resultingequivalent oxygen percentage across the posterior surface to thetargeted range of acceptable equivalent oxygen percentages.
 10. Themethod of claim 9, wherein the polymer layer of the contact lensconsists of a single polymer material.
 11. The method of claim 9,wherein the oxygen permeability of the component is zero.
 12. The methodof claim 9, wherein the component has a surface area greater than 38.48mm².
 13. The method of claim 9, wherein the component has a surface areagreater than 7.1 mm².
 14. The method of claim 9, further comprising asecond component, where the second component has an oxygen permeabilitylower than the oxygen permeability of the polymer layer.
 15. A method ofdetermining a thickness of a polymer layer of a contact lens, where thelens comprises an anterior surface; an opposing posterior surface; a lowor non-gas permeable component residing between the anterior surface andthe posterior surface; and a polymer layer between the component and theposterior surface; where the polymer layer has a thickness and an oxygenpermeability, where the component has an oxygen permeability lower thanthe oxygen permeability of the polymer layer, the method comprising thesteps of: estimating a first thickness of the polymer layer; performinga mathematical calculation or numerical simulation using the firstthickness to determine a first resulting equivalent oxygen percentageacross the posterior surface; comparing the first resulting equivalentoxygen percentage across the posterior surface to a targeted range ofacceptable equivalent oxygen percentages; estimating a second thicknessthat is larger than the first thickness if the first resultingequivalent oxygen percentage across the posterior surface is below thetargeted range of acceptable equivalent oxygen percentages; performing amathematical calculation or numerical simulation using the secondthickness to determine a second resulting equivalent oxygen percentageacross the posterior surface; comparing the second resulting equivalentoxygen percentage across the posterior surface to the targeted range ofacceptable equivalent oxygen percentages; estimating a third thicknessthat is smaller than the second thickness if the second resultingequivalent oxygen percentage across the posterior surface is above thetargeted range of acceptable equivalent oxygen percentages; performing amathematical calculation or numerical simulation using the thirdthickness to determine a third resulting equivalent oxygen percentageacross the posterior surface; and comparing the third resultingequivalent oxygen percentage across the posterior surface to thetargeted range of acceptable equivalent oxygen percentages.
 16. A methodof determining a thickness of a polymer layer of a contact lens, wherethe lens comprises an anterior surface; an opposing posterior surface; alow or non-gas permeable component residing between the anterior surfaceand the posterior surface; and a polymer layer between the component andthe posterior surface; where the polymer layer has a thickness and anoxygen permeability, where the component has an oxygen permeabilitylower than the oxygen permeability of the polymer layer, the methodcomprising the steps of: estimating a thickness of the polymer layer;iterating through the following process: performing a mathematicalcalculation or numerical simulation using the thickness to determine aresulting equivalent oxygen percentage across the posterior surface;comparing the resulting equivalent oxygen percentage across theposterior surface to a targeted range of acceptable equivalent oxygenpercentages; if the resulting equivalent oxygen percentage across theposterior surface is within the range of acceptable equivalent oxygenpercentages, exiting the iterative process; if the resulting equivalentoxygen percentage across the posterior surfaces is below the range ofacceptable equivalent oxygen percentages, increasing the thickness ofthe polymer layer and restarting the iterative process; and if theresulting equivalent oxygen percentage across the posterior surfaces isabove the range of acceptable equivalent oxygen percentages, decreasingthe thickness of the polymer layer and restarting the iterative process.17. The method of claim 16, where the polymer layer of the contact lensconsists of a single polymer.
 18. The method of claim 16, wherein theoxygen permeability of the component is zero.
 19. The method of claim16, wherein the component has a surface area greater than 38.48 mm². 20.The method of claim 16, wherein the component has a surface area greaterthan 7.1 mm².
 21. The method of claim 16, further comprising a secondcomponent, where the second component has an oxygen permeability lowerthan the oxygen permeability of the polymer layer.